Faqs

Normally standard foundations will be capable of dealing with the additional loads from the concrete floors in a domestic situation. Further advice should be requested in piled foundations or in multi storey situations.

Yes we can generally design the floors to carry solid walls. If you advise our sales personnel of your requirements at the enquiry stage you will be given the range of unit depths required for the various wall load options.

The maximum span of hollowcore floors will depend on the floor depth and the specific loadings imposed on the floor. Our technical department will be able to advise you on the most economic unit for your specific condition.

Reinforced concrete is manufactured from a combination of high strength concrete and normal reinforcement bars.

Prestressed concrete is a combination of high strength concrete and tensioned steel strands. This combination makes a very strong structural material that is used in the building of roof slabs, bridge girders and railroad ties. Prestressed concrete was invented and patented in 1886 by Henry Jackson, a San Francisco engineer. This type of concrete became the material of choice in Europe after World War II, due to the shortage of steel. The Walnut Lane Memorial Bridge, built in 1951 in Philadelphia, Pennsylvania, became the first structure in America made of this type of material.

Hollow core slabs are precast, prestressed concrete elements that are generally used for flooring. Some of their advantages are as follows:

• Long spans, no propping
• Flexible in design
• Fast construction
• Light weight structures
• Fire Resistant
• High load capacities
• Manufacture unique units specifically for your project

In most cases lintels carrying slabs are required to be 225mm deep. Stronger lintels are required for openings over 1800mm wide. Your architect/engineer should however be consulted as this is only a guideline.

Some building authorities recommend use of a suspended slab for structural reasons where depth of fill exceeds 600mm. Generally a suspended slab becomes the cheaper option where depths exceed 900mm. This however is dependent on availability of stone and labour.

SpanWright slabs have been used on various sites ranging from small semi-detached houses to large apartment blocks.

Walls can be built off SpanWright slabs in most cases. The type of wall construction depends largely on the span of the slabs. The SpanWright design division will indicate on each customer drawing whether concrete block, lightweight block or studwork partitions are suitable.

Generally foundations are capable of carrying the additional load without changing the design. Piled foundations sometimes require additional design. Please inform your engineer/architect that you are planning to use slabs, as early as possible.

Wider walls are usually only required where two slabs meet on a wall. Our design division will highlight any requirement for wider walls when producing a slab layout drawing.

Precast concrete floors are generally more expensive than timber joists. SpanWright’s special design makes them the most cost effective precast option. Overall cost will vary depending on the finishing method used. Additional costs can be as little as 10%. [Maurice Creighan (Local Building Contractor) reported that he saved one weeks labour per house by using SpanWright Slabs, therefore increasing speed and reducing labour costs.]